The Institute Chemistry, The Casali Center of Applied Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, 9190401, Jerusalem, Israel.
Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Leninskii prosp. 31, Moscow, 119991, Russia.
Mikrochim Acta. 2021 Apr 4;188(5):152. doi: 10.1007/s00604-021-04814-0.
The analysis of compounds of the nitroguanidine family at trace level poses an analytical challenge. Nitroguanidine, 1-methyl-3-nitroguanidine, and 1-methyl-3-nitro-1-nitrosoguanidine, which are addressed in this article, have low lipophilicity, with log(K) equal to -0.89, - 0.84, and 0.68, respectively, and as such are not amenable for preconcentration from water. Liquid-liquid extraction and SPE fail to concentrate them from water and it is also not possible to extract them by ion exchange resin even after a pH change. Nitroguanidine and 1-methyl-3-nitroguanidine nitramines are explosives of growing use and thereby growing environmental concern due to lower detonation sensitivity compared to RDX. A sensitive method for the determination of nitroguanidine, 1-methyl-3-nitroguanidine, and 1-methyl-3-nitroso-1-nitroguanidine by reduction to the respective amines and subsequent hydrophobization by derivatization with 4-nitrobenzaldehyde followed by LC-ESI-MS analysis is described. Reduction by sodium borohydride using palladium modified graphitic carbon nitride (Pd/g-CN) provided improved sensitivity compared to the traditional palladium modified activated carbon due to the lower adsorption of the reduction products on the carbon nitride substrate. The limit of detection of the method was 10 ng L for nitroguanidine, and repeated analyses of spiked effluents and contaminated spring water gave relative standard deviations of 8.8% and 6.5%, respectively. The findings illuminate the great promise of Pd/g-CN as a reduction catalyst for the determination of challenging hydrophilic organic contaminants.
痕量水平的硝胍家族化合物分析具有一定的挑战性。本文中所涉及的硝胍、1-甲基-3-硝胍和 1-甲基-3-硝基亚硝胍具有低亲脂性，其 log(K) 值分别为-0.89、-0.84 和 0.68，因此不适于从水中进行预浓缩。液液萃取和 SPE 均无法从水中浓缩这些物质，即使改变 pH 值也无法用离子交换树脂进行提取。硝胍和 1-甲基-3-硝胍是硝胺类炸药，由于其爆轰敏感度低于 RDX，因此使用越来越广泛，环境关注度也越来越高。本文描述了一种通过还原为相应的胺，然后用 4-硝基苯甲醛进行疏水化衍生化，再通过 LC-ESI-MS 分析来测定硝胍、1-甲基-3-硝胍和 1-甲基-3-硝基亚硝胍的灵敏方法。与传统的钯改性活性炭相比，使用钯修饰石墨相氮化碳（Pd/g-CN）作为还原剂，通过硼氢化钠还原，提供了更高的灵敏度，这是因为还原产物在氮化碳基底上的吸附较低。该方法对硝胍的检测限为 10 ng/L，对加标废水和受污染泉水的重复分析的相对标准偏差分别为 8.8%和 6.5%。这些发现阐明了 Pd/g-CN 作为测定具有挑战性的亲水性有机污染物的还原催化剂的巨大潜力。
